Just to contextualize your question, are you running your own CA?
EABs are used to associate an ACME account (which you are registering with a CA), with an external, non-ACME account that you already have (with that same CA).
Let’s Encrypt doesn’t use EABs, because there’s no concept of an “external account” - you just register an ACME account, and that’s it.
Different CAs, such as Sectgo, do use EABs. You create a Sectigo account, pay for some service, and then you can register any number of ACME accounts, linking each them to your Sectigo account with the EAB.
When I consider your questions, I’m not really sure how to answer them, without understanding some background of why you are asking about EABs to begin with.
Hope that kind of makes sense.